Fuel injection systems are known and mix fuel with air in internal combustion engines. Fuel is forcibly pumped through a fuel injector resulting in atomization of the fuel which is then mixed with air and is either indirectly or directly placed in the combustion chamber. The air-to-fuel ratio must be precisely controlled to achieve desired engine performance, emissions, and fuel economy. Electronic fuel injection systems control the amount of fuel injected by reacting to continuously changing inputs provided by various sensors, where each sensor's information is sent to an electronic control unit (ECU).
A known open loop electronic fuel injection (EFI) system is illustrated in FIG. 1. The known open loop EFI system 10 includes for example a fuel injector 12, an electronic control unit (ECU) 14, an air flow sensor (e.g. manifold absolute pressure MAP) sensor 16, communication circuitry 18 linking the ECU 14 and the MAP sensor 16 and communication circuitry 20 linking the ECU 14 and the fuel injector 12. Other components, that are known in the industry but not shown, include a fuel pump, a fuel pressure regulator, other various input sensors, which may include but are not limited to, a hall effect sensor, a throttle position sensor, a coolant temperature sensor, an oil temperature sensor, and other air flow sensors such as a manifold air temperature (MAT) sensor.
A known closed loop EFI system is illustrated in FIG. 2. The components of the closed loop EFI system 40 are generally the same as that of the open loop EFI system 10 except for the addition of an oxygen sensor 42 located in the exhaust system 22. Communication circuitry 44 links the ECU 14 and the oxygen sensor 42.
Common features known to both the open and closed loop EFI engine systems 10, 40 of FIGS. 1 and 2 include an exhaust system 22, an intake system 24, the engine 26, an alternator 28, and a gas tank 30. Air flow 32 enters at the intake system 24 and exhaust flow 34 exits at the exhaust system 22. Fuel 36 moves from the gas tank 30 to the fuel injector and is atomized. The atomized fuel 38 enters the intake system.
With further reference to the open loop EFI system 10, a MAP sensor 16 senses the amount of vacuum in the intake manifold and transmits this data to the ECU 14. The ECU 14 uses this information to determine the requested relative air-to-fuel ratio (AFR), which is a value set in the software, which will provide suitable engine performance. The ECU 14 electrically actuates the fuel injector 12 so that the atomized fuel 38 mixes with the air flow 32 to reach the requested relative AFR. Open loop EFI systems 10 do not receive any feedback as to whether the correct AFR is being achieved. Thus, the AFR may be incorrect due to any of the degradation of the fuel injector 12, the MAP sensors 16 becoming out of tolerance, etc. While an open loop EFI 10 is a lower cost system, the engine may not meet performance and emission requirements since there is not sufficient air/fuel mixture control to enable effective exhaust catalysis.
With further reference to the closed loop EFI system 40 of FIG. 2, the system 40 works in much the same way as the open loop EFI system 10 except for the addition of the oxygen sensor 42. The oxygen sensor 42 senses the amount of oxygen in the exhaust gas after combustion which is an indicator of whether the AFR is running at too high or too low a value. Data regarding the oxygen levels is transmitted to the ECU 14 and this information, along with information that may be available from other sensors, is processed and the amount of atomized fuel 38 injected is adjusted so that the actual AFR matches the requested relative AFR.
During full throttle conditions, on initial start-up, and during a transient occurrence (such as a load suddenly applied to the engine) the ECU 14 ignores inputs from the oxygen sensor 42, thereby mimicking an open loop state, and the engine 26 can produce more power by running an air-fuel mixture with greater (richer) amounts of fuel. Inputs from the oxygen sensor 42 are also ignored when the engine 26 is first started until appropriate operating temperatures are reached, wherein the time from start-up to oxygen sensor 42 input reading can be delayed from a minute to a couple of minutes, resulting in non-optimal engine performance. Closed loop EFI systems are known in the automotive industry.
It is known, in the automotive industry, to use a bump or projection or lack of projection on the crankshaft and/or camshaft to determine the position of the piston and when to start ignition. However, it is not known to incorporate a sensor to measure power output and/or power loads.
Other methods are still needed for optimizing the AFR and obtaining acceptable performance for an open loop or closed loop EFI system in a genset engine operating under a power load. Current genset engines are equipped with a simple ignition system that does not monitor current or voltage information and does not allow the controller to change spark timing.